A significant problem in producing MEMS condenser microphones with high yield is that the compliance and tension of the MEMS microphone diaphragm varies from one microphone to another.
Methods to calibrate the microphone after the fabrication process is completed are known. European Patent No. EP 1 906 704 A1 and U.S. Pat. No. 8,036,401 B2 disclose a method wherein the microphone is calibrated in a last step of the production process using an external reference sound source. However, this method has some disadvantages. It requires a high test effort and additional pins to read in the calibration results to the microphone. Moreover, it requires a non-volatile memory which is able to store the information determined in the calibration process even if the microphone is powered off. Such a non-volatile memory is expensive, space-consuming and difficult to realize in an integrated circuit.